Drafting apparatus and method



April 18, 1939. a FQSTER 2,154,675

DRAFTING APPARATUS AND METHOD Filed July 7, 1937 2 Sheets-Sheet l ATTORNEYS April 18, 1939. B. H. FOSTER 2,154,675

vDRAFIING APPARATUS AND METHOD Filed July 7, 1937 2 Sheets-Sheet 2 BY M #W ATTORNEYS Patented Apr. 18, 1939 UNITED STATES DRAFTING APPARATUS AND METHOD Boutwell H. Foster, Maplewood, N. J assignor, by mesne assignments, to United States Rubber Company, New York, N. Y., a corporation of New Jersey e Application July 7, 1937, Serial No. 152,312

5 Claims. (Cl. 19130) Asbestos yarn is widely used in the arts in the 1 making of fabrics for fire curtains and other fire proofing purposes, clutch facings, tapes, brake lining, and many other applications. In the method previously used for making commercial yarn, the relatively short asbestos fiber after passing through the usual preparatory operations, such as crushing, opening and cleaning, is mixed or blended with a small proportion of a vegetable fiber, usually cotton, and then carded. The percentage of cotton may be varied to some extent, but it is usually employed in the amount of about 15%. With a less cotton content than this, and the relatively short asbestos fiber stock 3;, in use, considerable difficulty has been had in the carding and spinning operations. However, recent improvements in carding and other operations have enabled spinnable rovings to be made containing as low as 8% cotton. In passing through the carding operation, the carded web is split into narrow strips which are thereafter compacted by rolling them between rub aprons to form rovings. The rovings are then passed through a pair of delivery rollers to a mule or ring spinning frame and spun without drafting. Accordingly, it has been necessary to prepare a different size of roving for the production of each different size of yarn. Hence, it is seen that the so-called spinning of prior commercial asbestos yarn is in reality merely a twisting operation.

Drafting systems as employed in the production of yarns from fibrous materials othenthan asbestos have not been applicable to the drafting of fiber length, lack of cohesion, and other characteristics of the asbestos fiber used. Asbestos yarns as prepared by prior commercial methods, are unbalanced, uneven, rough, loosely coinpacted, relatively coarse, and can be made only at a relatively low speed. Furthermore, the finest gauge of such asbestos yarn which it is feasible to manufacture on a commercial scale by the prior methods is about 35-cut, the same having a maximum twist of about 17 turns per inch, and such fine yarn could only be made by the use of the No. 1 grade fiber, or a mixture of this .and No. 2.

An object of the present invention is to provide 60 an improved apparatus and method for drafting asbestos rovings, due to the, weakiness, short relatively short fibers such as asbestos, which cannot be drafted by the usual apparatus employed for cotton and other longer staple fibers. Asbestos fibers in addition to being much shorter in length than cotton and wool fibers, have smooth slippery outer surfaces which causes them to slip one upon the other much more freely than cotton fibers which have a spiral tendency and wool fibers that have a scaley construction. This tendency of the asbestos fibers to slip relative to each other increases the tendency of the roving topull apart while being drafted.

Another object is to provide an improved apparatus and method for drafting relatively short fibers such as asbestos simultaneously with, and without injury to, longer staple fibers of other material which may be present in minor amount.

Another object is to provide an apparatus in which the distance between nips in drafting can be made relatively short without unduly reducing the diameter of the front rolls.

For a detailed disclosure of the nature and objects of the invention, reference is had to the accompanying specification and drawings, in which latter:

Fig. 1 is a diagrammatic side elevation of a suitable form of apparatus for carrying out the process of making the improved yarn;

Fig. 2 is a diagrammatic plan view of the drive mechanism for the various parts shown in Fig. 1;

Fig. 3 is a detail on a larger scale of a modifled form of drafting apparatus;

Fig. 4 is a similar detail of another modified form of drafting apparatus;

Fig. 5 is a similar detail of still another modification;

Fig. 6 is a similar detail of a still further and preferred modification; and

Fig. 7 is a similar detail of another preferred modification.

In a typical operation of the invention, an asbestos roving, which may be formed by the usual methods, may be led first, although not necessarily, through a wetting bath, then through the drafting mechanism of the present invention, and thence to a suitable twisting device such as an ordinary ring spinning frame, by which it is twisted and wound on a bobbin. If a wetting bath be used it serves to condense the roving, and, by the mutual cohesion of the fibers, to increase the resistance to drafting, whereby the drafting takes place smoothly and uniformly.

When, as may occur, the rovings are somewhat oily as a consequence of their method of manufacture, the wetting of the fibers may be aided by the inclusion of a suitable proportion of a textile wetting agent in the aqueous bath. The use of too great a concentration of such wetting so bons, sulphonated higher alcohols and esters, or

agent is to be avoided, as this tends to cause the absorption of so much water that the roving becomes swollen rather than condensed. Suitable concentrations of wetting agent are readily determined by experiment, examples of such being given hereinafter. Various wetting agents may be employed, such as those commonly employed for many purposes in the textile industry. Commonly used forms of wetting agents are salts, such as sodium salts, of sulphonated hydrocarsulphonated fatty oils, among which are the trade products AlkanoP and Gardinol, which are, respectively, a salt of a sulphonated naphthalene and a salt of a sulphonated higher alcohol, such as lauryl or oleyl alcohol. As as example, in the present invention Gardinol" may be used in a concentration of about 0.5%, or Alkanol in a concentration of about 0.2%.

It has also been found advantageous to add to the wetting bath, in addition to the wettin agent, a small proportion, such as 1%, of rubber latex unvulcanized or vulcanized, this amount of latex improving the spinning qualities of the roving but being indiscernible in the finished yarn. It is believed the latex acts to increase the resistance to drafting and/or make such resistance more uniform. Materials having equivalent properties may be used instead. However, excellent results may be obtained by wet drafting with water alone, or with water containing a small amount of glycerine.

The drafting apparatus is so constructed that any distance over which the asbestos roving is mechanically unsupported during its passage through the drafting mechanism is not substantially greater than the efiective mean length of the asbestos fibers in the roving, whereby the drafting is effected smoothly and without the formation of undue thick and thin places. The draft employed may be from 2: 1 up to as high as Suitable drafting constructions will be later set forth in detail.

The present apparatus and method, while equally applicable to drafting yarn from rovings made by the use of No. 1 or No. 2 grade of asbestos fibers, are more particularly applicable to'the drafting and twisting of relatively short staple asbestos fibers, such as have been previously used in making undrafted and twisted asbestos yarns in the range of sizes from 10- to 20- cut. Generally, the effective or virtual staple length of such asbestos fiber has been found to be approximately 0.5 inch. Aspecial advantage of the present invention is its application for spinning such short fibers as are known commercially as the No, 3 or spinning quality grade and are divided into various classes by means of a standard and well-known test which is as follows: Four superposed boxes are provided, the top one of which has a screen bottom with openings, the wire of the screen being of a diameter of .105". Below this box is a second box provided with a screen bottom of four meshes to the inch, the wire of the screen being of a diameter of -.063". Below this box is a third one having a screen bottom of ten meshes to the inch, the wire of which is of .047" diameter. Below this is a fourth box with an imperforate bottom. In testing a sample of asbestos fiber, one pound of the fiber is placed in the top box and the boxes are rapidly reciprocated for a period of two minutes, and the amounts of fiber remaining in each of the boxes are then weighed. The fourth box will contain the dust and fines.

Using the above test, the No. 3 or spinning quality grade of asbestos fiber is classified as follows:

Ounces per pound Class Box 1 Box 2 Box 3 Box 4 While any of the above classes of the spinning quality fiber, or their equivalent, may be utilized in the present invention: or mixtures of them, the preferred classes are Nos. 3 to 6. Classes 1 and 2 are more expensive and the supply too limited to be relied on for the commercial production, and Classes '7 and 8 contain such a large proportion of very short fiber asbestos that they are difflcult to card and make into yarn without the addition of an undesired amount of cotton fiber. In the present invention, it is preferred not to use more than 25% cotton, and this may be decreased to as little as 8% or 10%, the higher the percentage of longer fibered asbestos, the less amount of cotton required.

In Fig. 1, there is shown a diagrammatic side View of one form of cotton spinning mechanism as modified in the present invention. In this figure the numeral l designates a package of asbestos roving which is supported at one end by a suitable spindle to permit drawing off the roving with a minimum of tension. The roving 2 is led from the package over a guide 3 and. under a guide 4, the latter being disposed below the surface of a wetting bath in the receptacle 5. After passing through the wetting bath, the roving is led over a guide roll 6 and then passes through the drafting mechanism. This mechanism in the form shown consists of a lower back roll I, an upper back roll 8, a lower front roll 9, and an upper front roll 10, with a small intermediate roll ll disposed to press lightly against the upper back roll 8 and be frictionally driven thereby. The lower rolls I and 9 are the conventional fluted steel rolls, the upper rolls 8 and III are rubber covered, and the small roll H is a metal roll provided with small closely spaced circumferential grooves. The lower rolls 1 and 9 are positively driven while the upper rolls 8 and ID are idler rolls which are pressed against the lower rolls.

By the construction shown and described, the asbestos fibers of the roving, which roving may or may not be lightly twisted, after passing the nip of the back rolls 1 and 8, are gripped firmly enough at the nip between the small roll II and the upper back roll 8 to enable them to be drafted by the pull of the front rolls 9 and I0, while the cotton fibers are effectively gripped by the back rolls 1 and 8 and, because of their greater strength, are able to slip through the nip provided by the rolls H and 8. Thus the asbestos of that for the cotton flbers. The adherence of the wet roving to the auxiliary roll II also serves to prevent the asbestos fibers from being dragged ahead by the cotton fibers, thus aiding to prevent the formation of undue thick and thin places.

If additional main drafting rolls are employed, the small auxiliary roll I I may also be duplicated.

After it issues from the rolls 9 and Hi, the drafted roving passes through a pigtail guide I2, through the traveller l3 on ring l4, and is wound up as a twisted yarn on a bobbin IS on the spindle In Fig. 2 there is shown one form of drive mechanism for the apparatus disclosed in Fig. 1, said mechanism consisting of a motor I1 which through the belt l8 drives a pulley l9 on one end of a cylinder 20. Passing over this cylinder 20 are a series of drive belts 2| for the whirls 22 of the spindles I6. At the opposite ends of the cylinder 20 there is mounted a gear 23 which through the intermeshing gears 24, 25 and 26 drives a gear 21 carried by the front draft roll 9 at one end. At the opposite end of the front draft roll is carried a gear 28, which through the intermeshing gears 29, 30, 3! and 32 drives a gear 33 carried at the end of the rear draft roll 1.

The gear 25 is interchangeable, and by varying the. number of its teeth the speed of roll 9 can be varied, thus regulating the amount of twist being put into the yarn. The gear 30 is also interchangeable, and by varying the number of' teeth on this gear, the speed of the rear draft roll 1 may be varied to thus vary the draft, or the ratio of surface .speed of the front roll 9 to that of the rear roll I.

In Fig. 3 there is shown on an enlarged scale a modified form of drafting mechanism comprising a lower back roll 34, an upper back roll 35, a lower front roll 36, and an upper front roll 31. Extending around the lower rolls 34 and 36 is an extensible rubber apron 38, and a small idler roll 39' may be disposed to co-operate with the apron at a point between the front and back rolls. This small roll 39 may be entirely of metal such as steel. In'this form the lower 'rolls 34 and 36 are positively driven, while the upper rolls 35 and 31 are idler rolls and are covered with rubber in the conventional manner.

In the operation of this form of drafting mechanism the roving is fed between the upper back roll 35 and the apron 38, and is then carried by the apron to the nip between the upper front roll 31 and the apron, the roving being thus supported over the entire distance between the nips of the back and the front rolls. The pressure of the upper rolls against the apron and the lower rolls is suflicient to prevent the apron from slipping, whereby the pull exerted by the front rolls stretches the upper course of the apron in proportion to the ratio between the surface speeds of the front and back rolls,- the apron retracting upon leaving the lower front roll. Thus the roving and the'apron are drawn out to the same extent as they issue from the nip of the back rolls and there is substantially no relative motion between the upper course of the apron and the roving as the latter lies upon the apron.

The control of the fibers in this modification may be further increased if desired by the provision of the auxiliary small roll 39 which is disposed in contact with the upper face of the extensible'apron at a point intermediate of the back and front rolls.

In Fig. 4 there is shown a further modification rubberized fabric, extends around the lower front roll 42 and around a small auxiliary roll 45, so that the apron 44 provides a support for the roving over a substantial portion of its path between the front and back rolls. A second intextensible apron 46 passes over the upper front roll 43 and also over a second small auxiliary roll dl situated immediately above the first auxiliary roll 45. However, if desired, the second apron 46 may be omitted and the nip at the front of the drafting mechanism be provided directly between the top front roll 43 and the apron 44. In this form the lower rolls .40 and 42 are positively driven while the upper rolls 4| and 43 are idlers. The roll 4| may be rubber covered inthe conventional manner.

The drafts possible with asbestos rovings are relatively low as compared with other textile fiber materials, and hence the invention has been illustrated with the use of only two pairs of rolls in the drafting frame, since this number is adequate, but if desired, intermediate rolls may be used.

In Fig. 5 there is shown a form of drafting mechanism which essentially consists of a number of pairs of relatively small bottom and top rolls. In the drawings there have been illustrated four pairs of rolls but this number may be varied, if desired. In this form the rolls are preferably of a diameter approximately only onefourth that of the smallest rolls now in use in spinning'cotton, and spaced quite close together. For example, the rolls may be about A to of an inch indiameter. In Fig. 5 there are shown pairs of lower and upper rolls 48 and 49, 50 and 5|, 52 and 53, and 54 and 55. The lower rolls are positively driven at progressively greater speeds from back to front, while the upper rolls are idler rolls pressing against the lower rolls. All of the rolls are preferably fluted. It will be seen that in this form of the invention the roving is progressively drafted from the back pair to the front pair of rolls and at the same time the roving is never unsupported for a distance greater than the approximate effective length of the asbestos fibers.

In Fig. 6 there is shown another suitable form of drafting mechanism which is similar in some respects to that shown in Fig. 1 of patent to Casablancas No. 1,213,744. In Fig. 6 the numeral 56 represents a bottom driven back roll and 51 an idler top back roll. The numeral 53 designates the driven bottom front roll, and 59 an idler top front roll. Between the back and front rolls there is disposed a driven bottom roll 60 around which is disposed an endless rubber apron 6| which also passes around a fixed bar 62 of somewhat flattened contour. A co-operating upper apron mechanism comprises a roll 83, an endless rubber apron 64 and a flattened fixed bar 65.

In spinning frames of the type shown in Fig 1 of the Casablancas patent, the aprons or belts are made of thin leather, and they approach each other just closely enough to barely contact with the roving so as to support and feed it forward. Also the rodsor guidesl and 2 for the belts are widely spaced from each other (see Fig. 1 and p. l. 1. 57-61 of specification), so that at the line joining their centers the inner runs of the belts are spaced away from the rods. Hence the belts are as the pressure is insuflicient to grip the roving.

In practice the belts actually diverge before passing between the guides l and 2, and in the full size commercial machine the point of divergence is more than five-eighths of an inch from the nip of the front rolls. The belts are merely feeding belts, as the patentee terms them.

In the construction employed in Fig. 6 of the present invention, the belts or aprons 6| and 64 are relatively thick and made of rubber or soft leather and the spacing of the bars-or guides 62 and. 65 is close enough to press the belts together adjacent their point of divergence and cause the belts to firmly but resiliently grip the roving passing through them soas to frictionally hold it and cause the drafting of the asbestos fibers between the nip of the belts and the nip of the front rolls. The flattened bars 62 and 65 enable the nip of the belts to approach more closely to the nip of the front rolls, and the belts do not diverge from each other before reaching the forward edge of the bars, there being no clearance space between the belts. By reason of this construction the unsupported distance over which the roving passes from the front end of the belt nip to the nip of the front rolls is of the order of of an inch and preferably ahalf-inch or less. Hence the apparatus will successfully draft relatively short asbestos fibers.

In Figure 7 there is shown another desirable modification, which is similar in most respects to that shown in Figure 6. In place of the flattened guide bars 62 and 65 there are used round small diameter bars 66 and 61, or instead of stationary bars these bars may be in the form of small rollers. Also, it is preferred, both in the forms shown in Figures 6 and '7 to make either or both of the guide bars adjustable. One manner of accomplishing this is shown in Figure '7, in which the guide bar 61 is carried by a support may be adjusted in the frame support 10 by means of the nuts H. In operation the bars 66 and 61 will be adjusted closely enough together to cause a slight pressure on those portions of the belts 6| and 64 passing between the bars. This will enable sufiicient pressure to be obtained to provide a drafting nip. As before, the end of the nip provided by the belts 6| and 64 should notbe spaced more than about five-eighths of an inch from the nip of the front rolls 58 and 59, and preferably, the distance may be less. As in the case of the modification shown in Figure 6, the belts 6| and 64 may be made of rubber or soft leather.

As in the case of the modification shown in Figure 6, the construction shown in Figure '7 reduces the unsupported distance over which the roving passes from the front end of the belt nip to the nip of the front rolls to such an extent that the apparatus can be uilized for drafting extremely short fibers such as thosethat are contemplated to be used with the apparatus of the present invention.

In the asbestos art rovings and yarns are described in terms .of the number of yards per pound, and the word cut is used to designate a unit of yards. Therefore, this word, preceded by a number, indicates in multiples of 100 yards, the yardage per pound of a roving or a yarn. For example, a IO-cut yarn indicates that a pound of the yarn measures approximately 1000 yards; 18-cut indicates a yarn that measures approximately 1800 yards per pound. A very large proportion of the woven asbestos products of commerce are made from 10-cut yarn. In prior asbestos yarn manufacture, yarns from about 20-cut to 35-cut, the latter being about the finest commercially made, are made either from No. 1 grade asbestos fiber or No. 1 mixed with No. 2 grade. The Nos. 1 and 2 grades of asbestos are very scarce and expensive, and even when using these the yarns have been made from rovings of the same size as the finished yarns, without drafting but merely by twisting the roving, so that the cost of both material and manufacture is high.

As illustrating the advantages of the invention over the prior art, the following examples are given of drafted asbestos yarns made by the 68 provided with threaded extension 69, which apparatus and method of the p t nvention.

Table I I Roving Ya r n strgfiml' 512 1122 Gauge 'lwist Example cut size Draft sing e e a ive (nominal) gg fi sargngi strength ggg i (1cm Per inch No. 1 Canadian Crude 10 None 9 2. 2 20- 6. 3 .047 c 18 None 18 1. 4 25 4. 8 040 6 28 NODB 1. 7 48 5. 6 023 12 35 None 37 1. 2 44 4. 3 015 17 1O 2 13 2. 6 47 7. 5 029 13 10 2 212 3. 3 73 6. 3 028 12 1O 3. l 26 2.4 52 4. 4 016 14 10 5. 3 55 1. 5 83 4. 2 013 20 15 3. 1 44 1. 3 43 3. 3 016 21 15 5. 3 '76 0. 66 50 '1. 6 O10 24 15 5. 3 66 0. 51 34 1. 8 011 45 17 Z. 1 37 1. 3 43 2. 7 017 13 17 3. 1 51' 0. 90 46 2. 1 014 19 19 3. 1 62 1. 1 68 2. 9 011 22 19 5. 3 0. 44 48 1. 6 008 32 19 5. 3 0. 40 48 l. 3 007 27 19 5. 3 028 38 l. l 007 32 19 (2 ends) 5. 3 46 1. 5 69 5. 1 014 20 19 (2 ends) 3:1 31 2. 2 68 4. 4 L019 12 No. 1 Canadian crude is a commercial asbestos fiber averaging staple length.

Table II A B Percent Rov1ng- Strength AXB Example. cut size1 Draft 33% single Relative g gg g g g g (nomina (aqua-1) saigsnd strength break N o. 3 grade spinning quality fiber (Class 5) None 9 2. 0 18 8. 4 0. 039 6 2 20 1. 2 24 4. 2 021 11 3. 1 35 0.80 28 2. 0 020 14 5. 3 55 0. 53 29 1. 8 014 21 4 18 l. 5 27 7 .022 12 In the above tables the yarn of Example 5 was made with a concentration of 0.5% Gardinol in water as a wetting'agent, the yarn of Example 10 was made with the use of 0.5% Alkanol, and the yarns of Examples 6 to 9 and 11 to 24 inclusive were made with the use of 0.2% Alkanol. Also in Examples 8, 15 to 19 and 23 there was included 1% of a 25% concentration latex in the wetting bath. In the above tables Examples 1 to 4 and 20 are blanks and are given to show the characteristics of undrafted and unwetted asbestos yarns made by prior art methods. Obviously in an asbestos yarn made from an undrafted roving the cutsize should be the same for the finished yarn as for the roving, and it will be noted in the above tables that this is not strictly correct for Examples 1, 4, and 20. The discrepancy is caused by the fact that the nominal cut-sizes of the rovings used in these examples are the sizes as designated by the manufacturer of the roving, while the cut-sizes of the yarns produced were determined by actual weighing of measured lengths of yarn. The actual size of a roving may vary from the nominal size by. as much as 10% or more in either direction.

The figures given in the column headed "Relative strength give the strength in terms of a hypothetical l-cut'yarn, and accordingly aflord a comparison of the strength of yarns of different sizes on an equal weight-per-unit-length basis.

In the textile art the twist to be imparted to a yarn is ascertained by multiplying the square root of the yarn size by a predetermined number termed the "twist multiplier, or stated in another way, the twist multiplier is equal to the number of twists per inch divided by the square root of the yarn size.

roving of a nominal cut-size of '35 had an actual cut-size in the finished undrafted 'yarn of 37, and the twist per inch was 17, giving in this case a twist multiplier of 2.8. Due to the relative stiffness of the asbestos fibers in commercial asbestos rovings, most of the asbestos yarn produced heretofore has been made with a twist multiplier of 2 or less, in order to obtain a yarn more or less balanced which does not kink, and it has been impractical in any case to use a twist multiplier higher than about 2%. However, it will be noted that the wetting out of the fibers makes them softer and more pliable whereby a substantially higher twist multiplier can be employed without seriously affecting the balance or kink condition, and that the finished yarn is denser and for the same cut-size is smaller in gauge than the undrafted yarns of the prior art. For instance, in Example 5 the twist per inch was 13 and the cut-size of the yarn was 18, which gives a twist multiplier of 3; in Example 9 the twist per inch was 21 and the cut-size of the yarn was 44, which gives a twist multiplier of 3.2;. in Example 11 the twist per inch was 45 and the cut-size of the yarn was 66, which gives a twist multiplier of 5.5; in Example 12 the twist per inch was 18 and the cut-size 37, which gives a twist multiplier of 3; in Example 15 the twist per inch was 32 and the cut-size 110, which gives a twist multiplier of 3; and in Example l8 the twist per inch was'20 and the cut-size 46, which gives a twist multiplier of 3.

In order 'to furnish a still plainer basis for comparison of the superior products of the present invention with those of the prior art a series of yarns were made from the same batch of 10-cut roving of No. 1 Canadian asbestos fiber, the analysis of which yarns is shown in the following table:

Table III A B Percent Roving- Strength, AXB Example cut sizel Draft 33% stingl:l lielatlgle fi g g 633g? g gg (nomma (actual) s (118511.) 8 reng break 10 a. 1 2e 2. 4 e2 4. s o. 022 12 10 3. 1 24 1. 4 34 3. 9 027 12 10 None 10 2. 3 23 3. 3 029 5 10 None 8 2. 1 17 6. 1 056 6 10 (2 ends) 2. 1 8 8. 1 65 3. O 030 6 F 10 (3 ends) 3.1 9 4. 5 41 2. 2 .031 6 In examples B and D no wetting was used.

As previously stated, the finest asbestos yarns which it has been practicable to manufacture on a commercial scale by prior methods using no drafting is about 35-cut, with a maximum twist of about 17 turns per inch. In prior art Example 4 of Table I, it will be noted that a i In Examples A, C, E and F the fibers were wet by using a 0.2% concentration of Alkanol in water plus 1% of a 25% concentration latex.

Comparing Examples D, C, B and A, it will be seen that in prior art Example D, using neither drafting nor wetting, the relative strength or strength factor was 1'7, in C using wetting but no draft the relative strength was 23, in B using draft but no wetting the relative strength was 34, while in A using both draft and wetting the relative strength was 62.

In Examples B and A there is clear evidence of the advantage of using wetting for the drafting. In both examples the draft and twist were identical, and the yarn cut-sizes were very close, considering that'the same uniformity cannot be obtained with asbestos fibers as with ordinary textile fibers such as cotton. However, it will be noted that the relative strength of the drydrafted yarn B was 34, while that of wet-drafted yarn A was 62. It will also be noted that the gauge of yarn B was .027, while that of yarn A was .022, indicating that in the wetted yarn the fibers had been drawn more in parallel and were better compacted.

In Examples D, E and F the purpose was to compare an undrafted prior art yarn with drafted yarns, using the same twist and as nearly as possible the same cut-size of finished yarn. It will be noted that in prior art undrafted and unwetted Example D the relative strength was 17, while for drafted and wetted Examples E and F it was 65 and 41, respectively. These same examples further indicate the value of the drafting and wetting in increasing compactness, since in the undrafted Example D the gauge was .056, while in drafted and wetted Examples E and F the gauges were .030 and .031, respectively.

A desirable use of the invention is the drafting and twisting of two or more rovings to form a single yarn as illustrated in Examples 18 and 19 of Table I, Example 24 of Table II, and Examples E and F of Table III. By drafting two or, more rovings and increasing the amount of draft a multiple roving yarncan be obtained of the same cut-size as that obtained from a single roving with a less amount of draft, and at the same time the roving is much more uniform and the breaks or ends down are decreased. For instance, two rovings of 20-cut size may be given a draft of four to produce a finished yarn of: approximately 40-cut size, instead of employing a single roving of 20-cut size and giving it a draft of two to produce a finished yarn of approximately 40-cut size. The yarn made from the multiple roving with increased draft will, as before stated, be more uniform, and the number of ends down be considerably reduced.

It will be seen that by the use of the invention the manufacture of asbestos yarns of various sizes is greatly simplified, and also cheapened, inasmuch as a wide range of sizes of yarn may be produced from a single size of roving, merely by varying the speeds of the draft rolls. For example, from a -cut roving there may be made any smaller size of yarn down at least to 55-cut, the latter being materially finer than any heretofore produced. Similarly, by the use of a smaller roving, such as 19-cut, there may be made asbestos yarns of extremely fine gauge, such 'as 60-cut to 135-cut, which yarns are comparable in size with ordinary sewing threads and greatly extend the field of use of asbestos yarns. The yarns produced by the invention are well balanced and may be given a much higher twist, especially in finer sizes.

It has also been found that higher spindle speeds may be used without increasing the frequency of breakage, and that a greater yardage of yarn of a given cut-size may be wound on a single bobbin.

The yarns made by the present apparatus and process are also smaller and more compact than yarns of the same cut-size made by present commercial methods, and are at least 50% stronger, for yarns of the same cut-size. Furthermore, by the use of the invention low quality asbestos fiber, previously used only for the production of coarse yarns, may be made into fine yarns of relatively greater strength. Yarns of greater uniformity may be made according to the invention by drafting and twisting together a plurality of asbestos rovings to form a single yarn.

Since in the asbestos art the term asbestos is applied not only to products containing asbestos solely but also to products containing a minor amount of vegetable or other fiber, in the claims it is intended that the expressions asbestos roving" and specifically limited, shall include asbestos rovings and yarns in which small amounts of other fibers such as cotton, wool, glass, etc., may be included. Also, while particularly adapted for the use of short staple asbestos fiber, the invention is capable of use withother short fibers which cannot be drafted by the use of prior art apparatus and methods.

While specific embodiments of the invention have been shown and described, it is obvious that modifications may be made therein without departing from the spirit thereof, and it is not desired to limit the invention otherwise than as set forth in the appended claims.

Having thus described my invention, what I claim and desire to protect by Letters Patent is.

1. A method of making asbestos yarn which comprises wet drafting, with an unsupported spacing between successive nips of not substantially more than five-eighths inch, an asbestos roving the asbestos fibers of which have an average staple length not exceeding three-quarters of an inch, and twisting the drafted roving into a yarn.

2. A method of making asbestos yarn which comprises attenuating by wet drafting, between successive nips having not substantially more than five-eighths inch unsupported spacing, the asbestos fibers of an asbestos roving containing a minor amount of longer staple fibers of another material and which asbestos fibers are in major part capable of passing a screen of one-half inch opening, simultaneously therewith drafting said longer staple fibers, and twisting the drafted roving into a yarn.

3. A method of making asbestos yarn which comprises doubling and attenuating by wet drafting a plurality of asbestos rovings between successive nips having not substantially more than five-eighths inch unsupported spacing, the asbestos fibers of which rovings have an average staple length not exceeding three-quarters of an inch, and twisting the drafted assembly into a yarn.

4. A method of making asbestos yarn which comprises doubling and attenuating by wet drafting, between successive nips having not substantially more than five-eighths inch unsupported spacing, the asbestos fibers of a plurality of asbestos rovings containing a minor amount of longer staple fibers of another material and which asbestos fibers are in major part capable ofpassing a screen of one-half inch opening, simultaneously therewith drafting said longer staple fibers of said rovings, and twisting the drafted assembly into a yarn.

asbestos yarn, unless otherwise 5. A method of making asbestos yarn which comprises wet drafting an asbestos roving the asbestos fibers of which have an average staple length not exceeding three-quarters of an inch,

by delivering the roving between successive nips having a. predetermined speed differential and which exerta firm pressure upon the roving at the nip points arranged not substantially more than flve-eighths of an inch apart so as to give a definite control of the drafting of the short asbestos fibers, and twisting the drafted roving into a yarn.

BOUTWELL H. mm. 

